Calorie Deficit Calculator

Plan a moderate calorie deficit. See how many calories a day you'd eat with a deficit of 250 or 500 calories, about how much weight that could mean per week, and, if you want, roughly how long it would take to reach a goal weight.

An estimate for healthy adults

These formulas don't apply to people under 18, during pregnancy or breastfeeding, or with medical conditions that affect metabolism or weight. Talk to a doctor or registered dietitian before changing how you eat.

Calories with the deficit (kcal/day)

1,623

Calories you burn per day: 2,123 kcal/day
Change per day: −500 kcal
Approx. change per week: −1 lb
Weeks to your goal weight: —

Results are estimates for information only and do not constitute financial, medical, or legal advice.

How it works

The calculator estimates the calories you burn per day (your TDEE, with the Mifflin-St Jeor equation and your activity level) and subtracts the deficit you choose. About 7,700 calories equal 1 kg (3,500 per pound), so it also estimates the weekly change and, if you enter a goal weight, the number of weeks. These are averages; real progress is rarely a straight line.

The formulas

Calories = TDEE − deficit (250 or 500)

Weekly change ≈ deficit × 7 ÷ 7,700 (kg)

Worked example

A 30-year-old woman, 65 kg (143 lb) and 165 cm (5 ft 5 in), moderately active, with a 500-calorie deficit.

TDEE: about 2,124 calories a day.
With the deficit: about 1,624 calories a day.
Approximate change: 500 × 7 ÷ 7,700 ≈ 0.45 kg (1 lb) a week.

Sources

Harvard Health Publishing.Calorie deficit explained: Is it a safe, sustainable approach to weight loss?(a 500-calorie daily deficit as a starting point, and losing no more than 1 to 2 pounds a week).
Mifflin MD, St Jeor ST, et al.A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition, 1990.

Frequently asked questions

What is a calorie deficit?

Eating fewer calories than your body burns. Over time, the difference comes from stored energy, and body weight goes down. A deficit of about 500 calories a day is a common starting point for gradual weight loss.

Why not a bigger deficit?

Very large deficits are hard to keep up, make it harder to get enough nutrients, and can cause muscle loss. That's why this calculator only offers 250 or 500 calories a day and never goes below 1,200 calories for women or 1,500 for men. Larger cuts should only be made under medical supervision.

Why did my weight loss slow down?

As your weight goes down, your body burns fewer calories, so the same intake creates a smaller deficit. Water and other changes also make weight go up and down from day to day. Recalculate from time to time, and talk to a health professional if you have questions.